1. Technical Field
The present invention relates to a vehicle body attitude control apparatus for use in, preferably, a vehicle such as a four-wheeled automobile.
2. Description of the Related Art
Generally, there is known a vehicle body attitude control apparatus configured to reduce a roll rate by calculating lateral acceleration from a steering angle and a vehicle speed of the vehicle, obtaining lateral jerk by differentiating the lateral acceleration, and switching damping forces of the respective suspensions of the front, rear, left, and right wheels according to the lateral jerk (for example, refer to Japanese Patent Application Public Disclosure No. 2007-290650).
Further, there is also known an apparatus capable of achieving a target behavior of a vehicle body to stabilize the attitude of the vehicle body by obtaining a target roll angle from lateral acceleration while the vehicle is running, calculating a target pitch angle according to the target roll angle, and performing feedback control (FB control) by obtaining a difference between an actual roll angle and an actual pitch angle (for example, refer to Japanese Patent Application Public Disclosure No. 2007-170590).
On the other hand, a driver's feeling during a steering operation of a vehicle has been studied by various researches until now, as indicated in, for example, non-patent documents 1, 2, and 3 listed in “LIST OF NON-PATENT DOCUMENTS” which will be provided below. The non-patent document 1 focuses on the relationship between a roll angle and a pitch angle while the vehicle is running, and discusses that reducing a phase difference between a roll angle and a pitch angle can improve a driver's feeling such as a ride comfort and steering stability that the driver feels on the vehicle. The non-patent document 2 discusses that a driver can have a good feeling toward a roll behavior accompanied by head-down pitching when the driver operates the steering wheel. Further, the non-patent document 3 discusses that a driver can have a good feeling if the rotational axis hardly wobbles with a roll behavior and a pitch behavior of the vehicle in harmony with each other.
The contents of these non-patent documents 1 to 3 can be generally divided into two points as indicated by the following items (1) and (2).
(1) A phase difference between a roll angle and a pitch angle is small.
A phase difference between a roll rate and a pitch rate is small.
The roll rate and the pitch rate are in a proportional relationship.
The rotational axis of a roll motion and a pitch motion is stabilized, and especially, the non-patent documents 1 and 3 indicate that the rotational axis of rolling and pitching hardly wobbles.
(2) The non-patent document 2 indicates a roll behavior accompanied by head-down pitching.